Genetics and heredity – nowadays, everyone knows that diseases can be inherited. For that very reason, patients seek advice with their doctors because they are concerned about unborn children, family members, or themselves. An aspiring doctor must therefore be able to provide genetic counseling and diagnosis. The following article addresses the different modes of heredity, explains important tools –e.g. family pedigree creation and analysis–, and illustrates their application using the example of cystic fibrosis, a frequent genetic disease.

00:01
Now, a quick lecture on genetic counseling and prenatal diagnosis. The field of genetic counselingor clinical genetics has changed a lot in recent years due to the advent of all these new technologiesand the discovery of more and more genes. But it is going to involve things like counselingand taking family histories which is more traditional, as well as calculating risk assessmentsand pedigree analysis, molecular diagnostics and the whole genome diagnostics. These techniquesall come together. Generally now, we have genetic counselors that take care of the genetic counselingpart of the practice. But either way, in considering genetic counseling, whichever degree of itthat you might get into, you would be considering not only the original patient but we needto be concerned with the future children of that patient as well as other family members of that patient.
01:09
These are all the people that come into the picture when genetic counseling for one individual.
01:16
Not only do we need to consider the diagnosis part but we also need to consider the psychologicalaspects as well as social aspects and medical aspects of treating or managing genetic disorders.
01:33
So, this is now the whole field of clinical genetics. As I said, the majority of times, this is taken care ofby genetic counselors. Genetic counseling is a burgeoning field now in the United States, the UK,and Canada. Very common if someone goes in and has a family history, say of breast canceror a colon cancer for the doctor to refer them to genetic counseling. A lot of this can be doneby sending in samples. You can send them in from your regular doctor. As a doctor, you would perhapsbe in charge of taking samples and sending them and then referring the client out to genetic counselingmuch as you would work with other members of a team, surgeons, and internists, and so onand so forth in order to provide a full spectrum of genetic care. Today, both the United Statesand Canada have specific boards of genetic counselors. People become board-certifiedgenetic counselors. Often they’re nurses or physician’s assistants that specialize in geneticsbut they don’t necessarily have to be in those particular roles. They could be purely in the roleof genetic counseling because clearly, genetic counseling not only entails counselingand the genetic diagnosis but lots of other fields as well. So, it’s becoming a very, very specialized filed.
03:10
As a doctor yourself, you probably won’t be involved in too much of the detail of genetic counselingbut referring patients is most important. Who should be referred for genetic counseling?You probably are pretty familiar with anyone having a family history. If you’ve got to an adult life,anyone having a family history of genetic disorder would be a great candidate for genetic testing.
03:35
Of course, in considering referring for genetic testing, you want to consider their own backgroundand values and whether it’s something that’s suitable for them. Ultimately, it is the patient themselvesthat would make that decision. Now, it’s highly recommended that women interested in becomingpregnant or having a pregnancy over 35 years of age have genetic counseling because there are so manytests available to us now. We can do preimplantation genetic diagnosis, all sorts of techniques to preventimplantation of an embryo that may have genetic predisposition or actual genetic mutation itself.
04:24
Of course, we might want to refer a mother who’s had repeated miscarriages or has had a previous childwith a genetic disorder so that we can also do some work on the frontend to prevent implantationof an embryo that has defects. As we’ve explored before in the molecular genetics course,there are so many techniques available for genetic diagnosis including gene panels where we canexamine hundreds of genes at a time, sort of probe for genes. Targeted sequencing where we can say,hey, does this person have this particular gene and target probes to that to label them as we see in FISH.
05:09
Whole exome sequencing, so we take all the exons and sequence those to see what genes might be there.
05:18
Then, whole genome sequencing; now, with the dropping cost of whole genome sequencing,that is going to become more of a viable option for genetic counselors and doctors alike.
05:32
All of these advents in DNA technologies have really lent themselves to a bright future for genetic testing.
05:42
Thinking about whole genome sequencing, this is a graph from National Institute of Healthand the Human Genome Research Institute. I thought I’d do a quick search and see how the priceshave changed over the years. For example, back in 2006, it cost 20 to 25 million dollars to sequenceone human genome. By the end of 2015, the price had dropped to below $1,500.
06:13
In the beginning of 2016, I think it hit its first sub $1,000 cost per person to sequence a genome.
06:23
It’s becoming more and more available and more and more of a cost effective techniqueto sequence a whole genome. I think with the advent of whole genome sequencing,we need to keep our eyes open for the possibilities that it can offer us.

About the Lecture

The lecture Genetic Counseling by Georgina Cornwall, PhD is from the course Population Genetics.

Included Quiz Questions

Which of the following is not a diagnostic aid in genetic relativity of a disease?

Blood picture

Family history

Pedigree analysis

Genome diagnostic

Molecular diagnostics

Which malignancy requires genetic counselling most?

Colon cancer

Burkits lymphomas

Non Hodgkin lymphoma

Small cell carcinoma of the lung

Hepatic carcinoma

Which of the following women would most require genetic counselling?

Pregnant over 35 years of age

Pregnant under 20 years of age

Women in there 6th pregnancy

Women in their 10th pregnancy

Women with IVF

What is the most detailed procedure for detection of early predisposition to genetic disorders?

Whole genome sequencing

Whole exome sequencing

Gene panels

Family history

Targeted sequencing

Author of lecture Genetic Counseling

Georgina Cornwall, PhD

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